What Is a Vented Pipe Wall Gauge?

About Vented Pipes

• Vented pipe refers to pipe that allows air in or out of a plumbing system. Vent pipes are also known as vent stacks. Vent stacks usually have access to fresh air on the roof and connect with every drain inside the house. Without vents, the negative air pressure inside pipe drains would create clogs, and liquid would not flow downstream. Vents allow the air pressure to change inside the pipe and for liquids to drain freely.

About Pipe Gauges

• Pipe gauge refers to the thickness of the pipe walls. In pipe gauges, the lower the number, the thicker the wall is. A pipe gauge of 1, for example, has a wall thickness of about .3 inch, while a pipe gauge of 36 has a pipe wall thickness of about .004 inch. The gauge of a pipe relates to the job that it is tasked with. Sewer pipes generally have a thicker gauge, and pipes that carry air usually have a thinner gauge, as the wall of the pipe does not have to be as strong.

Identifying Pipe Gauge

• Most pipes have a gauge printed on the side of the pipe. Pipes are gauged at the factory and marked with printed ink or laser engravings, depending on the type of material. Schedule 40 PVC pipe, for example, typically has blue or red ink printed on the side. A copper pipe might have black ink. Pipe gauges are typically expressed in terms of the gauge number, followed by GA. For example, a 12-gauge pipe should be marked as "12GA."

Copper Gauges

• Some copper pipes are color-coded to make identifying their gauge easier. Instead of numbers, these pipes are assigned letters to identify wall thickness. Colored copper pipes comes in red, green, blue and yellow. Red pipe is known as M pipe and has the thinnest walls of any copper pipe. Green pipe is known as K pipe and is the thickest pipe available. Blue pipe is known as L pipe and has an intermediate wall thickness. Yellow is for drainage and waste lines, and is the most likely color to be used for vent plumbing due to its intermediate wall thickness and large diameter.